Electric heating unit for drying hood

ABSTRACT

A heating unit for use in a drying hood comprises a radial flow fan surrounded by at least one annular electric heating element. The heating element comprises a metallic supporting wire core having glass filamentary insulating material wound thereabout and a thin heating wire wound about the insulating material. The heating element is secured by a plurality of holding straps between a pair of annular plates of electrically insulating material spaced a short distance apart whereby a compact heating assembly of low heat output can be achieved. The straps and electrical components associated with the fan motor and heating elements may all be secured to one of said plates. One of the straps provides an electrical connection for a motor tapping to the heating element.

7/1925 Furfaro et al 219/355 X 9 Unite States Patent 1 1 1 1 3,840,723 Ohnmachtet a1. Oct. 8-, 1974 1 ELECTRIC HEATING UNIT FOR DRYING 1,979,883 11/1934 Hymes 219/369 HOOD 2,221,045 11/1940 Edington 219/370 X 2,408,33l 9/1946 M1115 219/400 [7 1 Inventors: Helmut Ohnmacht; Klaus y 2,411,782 11/1946 Gardes.... 219/370 both of Kandel/Pfalz, Germany 3,223,828 12/1965 Mast 219/375 X 1 488191164 Fritz Kandel/Pnn 33531322 1111322 111 1131131311::iijijiiijii....1133: 513/??? Germany 13,497,675 2/1970 Yoshike et al. 219/364 UX [22] Filed: July 7, 1972 Primary Examiner-A. Bartrs PP No 269,740 Attorney, Agent, or Firm-Craig & Antonelli [30] Foreign Application Priority Data [57] ABSTRACT Sept. 4, 1971 Germany 2144361 A heating unit for use in a drying hood cOmprises a radial flow fan surrounded by at least one annular [52] US. Cl 219/368, 34/99, 165/125, electric heating elemwt- The heating element 219/364, 219/370, 219/376, 219/542, 338/302 prises a metallic supporting wire core having glass fila- [51 I (jl 05b 3 00, 45 20 33 244 3 04 mentary insulating material wound thereabout and a [58] Field of Search 219/366-371, thin heating wire wound about the insulating material- 2 9 374 37 3 59 4 3 53 3 5 5 57 400 The heating element is secured by a plurality of hold- 379 3 2 542 54g 551; 1 5 24 2 ing straps between a pair of annular plates of electri- 3 3 /3 2 305 315 317420 323425 332; cally insulating material spaced a short distance apart 334 9 40 12 25 257 whereby a compact heating assembly of low heat outpm Can be achieved. The straps and electrical compo- 5 References Cited nents associated with the fan motor and heating ele- UNITED STATES PATENTS ments may all be secured to one of said plates. One of l 399 688 12/1921 C t l 219,370 X the straps provides an electrical connection for a 1:531:515 3/1925 51:222.?if 11:12:11.... 219/370 motor tappmg to the heatmg element 1,547,647

15 Claims, 4 Drawing F igures- ELECTRIC HEATING UNIT FOR DRYING HOOD The invention relates to a heating unit of the kind having a radial-flow fan with an annular air outlet surrounded by an annular heating element. Heating units of this kind are provided in drying hoods, e.g. for hair drying.

The tendency nowadays in the heating appliance art is towards constructional forms of ever smaller size, so as to make the appliances handy to use and to enable them to be stored without requiring a great deal of space. The appliance housings are also generally made of plastics material which, as is shown, can only withstand a limited temperature. For this reason, in such appliances the heating power is reduced to an increasing extent so as to avoid damage to the housing. But reducing the overall size and the heating power give rise to conflicting requirements in regard to the construction of the heating unit.

In known heating units, the heating element consists ofa helically coiled heating wire which surrounds the annular air outlet in annular manner. Usually a plurality of wire coils are arranged above one another'and adjacent one another within an annular chamber. Since the heating wire coils expand when heated, they tend to sag. In order to prevent the wire coils from contacting one another, they have to be supported at several places within the annular chamber, which is effected for example with the use of ceramic supports which guide and support the heating wire coil in holes. These supporting ceramic plates constitute insertswhich are an obstacle to flow, and have a disadvantageous effect on the fan which is upstream of them and on the efficiency of the drying hood.

Neither the overall size nor the power of the known heating units can be reduced to a desired extent. The reason for this is that on the one hand a fairly considerable spacing must be maintained between the coils,

which sets limits on the overall size, and on the other hand reducing the heating power involves reducing the wire diameter. This diameter reduction at the same time is prejudicial to the inherent stability of the heating wire coil, so that the latter sags to an even greater extent. Consequently, if the heating power is reduced, even more supporting elements must be provided so that the efficiency is impaired, and this is highly undesirable insuch small heating units.

The invention has as its object to construct a heating unit of the aforementioned kind in such a manner that it is possible to reduce the heating power to suit practical requirements whilst at the same time making it possible to reduce the overall size without efficiency losses.

This object is achieved according to the invention in that the heating element comprises a supporting core which has a thin heating wire wound about it and surrounds the air outlet ring in annular manner, the wirewound core being arranged between two plates of insu' lating material with small spacing, and being secured by means of a few holding straps.

The heating element constitutes a structure which is stable in itself, so that the diameter of the wire can be reduced to a minimum without thereby giving rise to a risk of short-circuiting. For this reason the flow duct can also be given a low height since the spacing of the insulating material plates need only be slightly greater than the diameter of the heating element. Finally, it is only necessary to provide a few holding straps constituting obstacles to flow, and these can moreover be made desirably narrow since they only fix the wire heating element in position but do not need to support it.

In a preferred embodiment of the invention two such heating elements are provided concentrically with respect to one another. This does not add to the height of the flow duct although it does involve a widening which does not detrimentally affect anything else.

The holding straps are preferably provided in the form of narrow spring clips such that the annular heating element can be inserted into the clips. The invention also provides the possibility that the holding straps, all connecting contacts, a temperature switch, and a resistance section providing a tapping for a fractionalhorsepower motor of the fan, are fixed to one of the insulating material plates. This gives a constructional form which is particularly advantageous from the assembly point of view, since almost all of the parts can be attached with rivets or eyes to a single plate.

A constructional form which is space-saving and advantageous as regards its dimensions is, moreover, ob tained if a holding strap made of metal at the same time forms a connection for the motor tapping. Finally, the necessary connecting leads for the heating unit and also the resistance section can consist of metal strips which can be arranged in a particularly simple manner on the plate of insulating material.

Further details, featuresand advantages of the invention are shown in the following description of a preferred embodiment, with reference to the accompanying drawings in which:

FIG. 1 is an axial section through the upper part of a drying hood;

FIG. 2 is a plan view of. the underside of a carrier plate ofa heating unit shown in FIG. I; and

FIG. 3 is a section taken on III/III of FIG. 2.

FIG. 4 is a cross-section of the heating wire of this invention.

The drying hood which is shown in FIG. I is designed for hair drying. It comprises a housing made of plastics material which as a whole is given the reference numeral l and in which there is arranged a fractionalhorsepower motor 2 with a radial fan 3 in front of it. The radial fan draws air in through apertures 4 and delivers it as shown by arrows 5 into an annular heating duct 6. Arranged in the heating duct 6 is a heating element which as a whole is given the reference numeral 7. The air heated by this heating element is deflected by a curtain 9 into a substantially axial direction indicated by arrows 8 and passes through apertures in the hood part 10 into the interior of the hair-drying hood.

The heating element designated as 7 in FIG. I is arranged between upper and lower plates 11, 12 of insulating material, as illustrated in FIG. 3. As FIG. 4 shows more particularly, the said element comprises a supporting core 13 consisting e.g. of steel wire, about which an insulating material 13, e.g. glass filament material, is spun, whereas the actual heating wire 14 is wound on this insulation. The heating element 7 is arranged annularly about the air outlet ring of the fan 3, as FIG. 2 in conjunction with FIG. 1 shows. In the illustrated embodiment the heating element 7 is fixed by a total of three holding straps 15 which are connected by eyes or rivets to the upper insulating material plate 11.

F 3 These holding straps are constructed as spring clips with two generally parallel limbs 16, 17.

in the illustrated embodiment, the heating unit is a switchable two-stage unit, in which the annular heating element 7 isan inner element and is surrounded concentrically by an outer annular heating element 18. This latter heating element 18 is constructed and held in the same way as the former 7.

Connecting contacts 19, 20 and 21 are also secured as eyelets to the upper insulating material plate 11. This plate also carries an over-temperature switch 22. A connecting lead, in the form of a metal strip 23, is also attached by eyelet means to the insulating material plate 11.

Since appliances of the kind described are nowadays usually driven with fractional-horsepower motors of e.g. 12 volts, a resistance section is also provided as a motor tapping. This motor tapping is provided in the form of a metal strip 24, and a connection to it is effected at one end by means of one of the holding straps, e.g. the holding strap 25. The other end of the metal strip 24 is connected to an eyelet 25', similar to 19, 20 and 21, for connection to a fractional-horsepower motor.

We claim:

1. In a heating unit havinga housing, a radial-flow fan mounted in said housing, said fan being of the type having an axial air intake and providing radial air flow in an annular outlet path surrounding said fan, a heating element assembly and means for supporting said heating element'assembly in said housing with respect to said fan, the improvement comprising said heating element assembly including: I

at least one annular support core arranged concentrically about said fan' in the annular outlet path, thin-heating wire wound about said at least one support core,

two annular plates of insulating material for holding said support core annularly about said fan, said two plates being spaced apart by a small distance, such that said support core is held therebetween, and

a plurality of holding straps secured to at least one of said two plates for holding said support core between said two plates.

2. A heating unit according to claim 1, wherein at least a second annular support core having a thin heating wire wound thereabout is held by a' second plurality of holding strapsbetween said two plates, said at least second support core being concentric with said at least one support coreL 3. A heating unit according to claim 1, wherein said plurality of holding straps are in the form of narrow spring clips.

4. A heating unit according to claim 1, wherein said plurality of holding straps are all secured to the same one of said two plates.

5. A heating unit according to claim 1, further comprising connecting contacts for connecting said thin heating wire to a source of electrical energy, a temperature switch connected between one of said connecting contacts and said source of electrical energy, and a por- 4 tion of said heating wire forming a resistance section to provide a motor tapping for a fractional horsepower motor for said fan.

6. A heating unit according to claim 5, wherein said plurality of holding straps, said connecting contacts, and said temperature switch are all connected to the same one of said two plates.

7. A heating element according to claim 5, wherein one of said plurality of holding straps is made of metal and provides the electrical connection for said motor tapping to said heating wire.

8. A heating element according to claim 1, wherein one of said plurality of holding straps is made of metal and provides an electrical connection for a motor tapping to said heating wire.

9. A heating unit according to claim 1, wherein said at least one support core consists of a steel wire having an insulating material wound about said steel wire.

10. A heating unit according to claim 9, wherein said insulating material is a glass filament material.

11. A heating unit for use in a drying hood comprisa housing having an air inlet,

a radial-flow fan mounted in said housing with respect'to said air inlet to provide air flow through an annular air outlet duct concentrically surrounding said fan, and

at least one heating element assembly arranged in V said housing for concentrically surrounding said fan, such that said air flow through said annular air outlet duct flows over said heating element assembly, wherein said at least one heating element assembly comprises a supporting core, a thin heating wire wound about said core, and two annular plates of insulating material mounted in said housing, said plates being separated by a smalldistance and said core being disposed between the two plates by a plurality of holding straps secured to at least one of said two plates, whereby said at least one heating element assembly provides reduced heating power in a compact structure.

12. A heating unit according to claim 11,.wherein said holding straps are narrow spring clips.

13. A heating unit according to claim 11, wherein one of said holding straps is made of metal and serves as a motor tapping connection to said heating wire.

14. A heating unit according to claim 11, further comprising connecting contacts for connecting said thin heating wire to a source of electrical energy, a temperature switch connected between one of said connecting contacts and said source of electrical energy, and a portion of said heating wire forming a resistance .section to provide a motor tapping for a fractionalhorsepower motor for said fan.

15. A heating unit according to claim 14, wherein said plurality of holding straps, said connecting contacts; and said temperature switch are all connected to the same one of said two plates. l =i 

1. In a heating unit having a housing, a radial-flow fan mounted in said housing, said fan being of the type having an axial air intake and providing radial air flow in an annular outlet path surrounding said fan, a heating element assembly and means for supporting said heating element assembly in said housing with respect to said fan, the improvement comprising said heating element assembly including: at least one annular support core arranged concentrically about said fan in the annular outlet path, thin-heating wire wound about said at least one support core, two annular plates of insulating material for holding said support core annularly about said fan, said two plates being spaced apart by a small distance, such that said support core is held therebetween, and a plurality of holding straps secured to at least one of said two plates for holding said support core between said two plates.
 2. A heating unit according to claim 1, wherein at least a second annular support core having a thin heating wire wound thereabout is held by a second plurality of holding straps between said two plates, said at least second support core being concentric with said at least one support core.
 3. A heating unit according to claim 1, wherein said plurality of holding straps are in the form of narrow spring clips.
 4. A heating unit according to claim 1, wherein said plurality of holding straps are all secured to the same one of said two plates.
 5. A heating unit according to claim 1, further comprising connecting contacts for connecting said thin heating wire to a source of electrical energy, a temperature switch connected between one of said connecting contacts and said source of electrical energy, and a portion of said heating wire forming a resistance section to provide a motor tapping for a fractional horsepower motor for said fan.
 6. A heating unit according to claim 5, wherein said plurality of holding straps, said connecting contacts, and said temperature switch are all connected to the same one of said two plates.
 7. A heating element according to claim 5, wherein one of said plurality of holding straps is made of metal and provides thE electrical connection for said motor tapping to said heating wire.
 8. A heating element according to claim 1, wherein one of said plurality of holding straps is made of metal and provides an electrical connection for a motor tapping to said heating wire.
 9. A heating unit according to claim 1, wherein said at least one support core consists of a steel wire having an insulating material wound about said steel wire.
 10. A heating unit according to claim 9, wherein said insulating material is a glass filament material.
 11. A heating unit for use in a drying hood comprising: a housing having an air inlet, a radial-flow fan mounted in said housing with respect to said air inlet to provide air flow through an annular air outlet duct concentrically surrounding said fan, and at least one heating element assembly arranged in said housing for concentrically surrounding said fan, such that said air flow through said annular air outlet duct flows over said heating element assembly, wherein said at least one heating element assembly comprises a supporting core, a thin heating wire wound about said core, and two annular plates of insulating material mounted in said housing, said plates being separated by a small distance and said core being disposed between the two plates by a plurality of holding straps secured to at least one of said two plates, whereby said at least one heating element assembly provides reduced heating power in a compact structure.
 12. A heating unit according to claim 11, wherein said holding straps are narrow spring clips.
 13. A heating unit according to claim 11, wherein one of said holding straps is made of metal and serves as a motor tapping connection to said heating wire.
 14. A heating unit according to claim 11, further comprising connecting contacts for connecting said thin heating wire to a source of electrical energy, a temperature switch connected between one of said connecting contacts and said source of electrical energy, and a portion of said heating wire forming a resistance section to provide a motor tapping for a fractional-horsepower motor for said fan.
 15. A heating unit according to claim 14, wherein said plurality of holding straps, said connecting contacts, and said temperature switch are all connected to the same one of said two plates. 